[#1516] traverser: Check for placement vector out of range

Placement vector may contain fewer nodes count than it required by policy
due to the outage of the one of the node.

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

pkg/services/object_manager/placement/traverser.go

@@ -114,11 +114,11 @@ func NewTraverser(opts ...Option) (*Traverser, error) {
 		var unsortedVector []netmap.NodeInfo
 		var regularVector []netmap.NodeInfo
 		for i := range rem {
-			unsortedVector = append(unsortedVector, ns[i][:rem[i]]...)
-			regularVector = append(regularVector, ns[i][rem[i]:]...)
+			pivot := min(len(ns[i]), rem[i])
+			unsortedVector = append(unsortedVector, ns[i][:pivot]...)
+			regularVector = append(regularVector, ns[i][pivot:]...)
 		}
 		rem = []int{-1, -1}
-
 		sortedVector, err := sortVector(cfg, unsortedVector)
 		if err != nil {
 			return nil, err

pkg/services/object_manager/placement/traverser_test.go

@@ -356,6 +356,52 @@ func TestTraverserPriorityMetrics(t *testing.T) {
 		require.Nil(t, next)
 	})
 
+	t.Run("one rep one metric fewer nodes", func(t *testing.T) {
+		selectors := []int{2}
+		replicas := []int{3}
+
+		nodes, cnr := testPlacement(selectors, replicas)
+
+		// Node_0, PK - ip4/0.0.0.0/tcp/0
+		nodes[0][0].SetAttribute("ClusterName", "A")
+		// Node_1, PK - ip4/0.0.0.0/tcp/1
+		nodes[0][1].SetAttribute("ClusterName", "B")
+
+		sdkNode := testNode(5)
+		sdkNode.SetAttribute("ClusterName", "B")
+
+		nodesCopy := copyVectors(nodes)
+
+		m := []Metric{NewAttributeMetric("ClusterName")}
+
+		tr, err := NewTraverser(
+			ForContainer(cnr),
+			UseBuilder(&testBuilder{
+				vectors: nodesCopy,
+			}),
+			WithoutSuccessTracking(),
+			WithPriorityMetrics(m),
+			WithNodeState(&nodeState{
+				node: &sdkNode,
+			}),
+		)
+		require.NoError(t, err)
+
+		// Without priority metric `ClusterName` the order will be:
+		// [ {Node_0 A}, {Node_1 A} ]
+		// With priority metric `ClusterName` and current node in cluster B
+		// the order should be:
+		// [ {Node_1 B}, {Node_0 A} ]
+		next := tr.Next()
+		require.NotNil(t, next)
+		require.Equal(t, 2, len(next))
+		require.Equal(t, "/ip4/0.0.0.0/tcp/1", string(next[0].PublicKey()))
+		require.Equal(t, "/ip4/0.0.0.0/tcp/0", string(next[1].PublicKey()))
+
+		next = tr.Next()
+		require.Nil(t, next)
+	})
+
 	t.Run("two reps two metrics", func(t *testing.T) {
 		selectors := []int{3, 3}
 		replicas := []int{2, 2}